Process to prepare a gas oil fraction and a residual base oil

Abstract

The present invention provides a process to prepare a gas oil fraction, a heavy distillate fraction and a residual base oil fraction, which process at least comprises the following steps: (a) subjecting the feedstock to a hydroprocessing step to obtain an at least partially isomerised feedstock; (b) separating the isomerised feedstock by means of distillation into at least a gas oil fraction, a heavy distillate fraction and a residual fraction, wherein the residual fraction has a T10 wt % boiling point of between 200 and 450° C.; (c) recycling part of the residual fraction to step (a); and (d) catalytic dewaxing of remaining residual fraction to obtain a residual base oil.

1 . A process to prepare a gas oil fraction, a heavy distillate fraction and a residual base oil fraction from a Fischer-Tropsch derived feedstock, by
 (a) subjecting the feedstock to a hydroprocessing step to obtain an at least partially isomerised feedstock;   (b) separating the isomerised feedstock by means of distillation into at least a gas oil fraction, a heavy distillate fraction and a residual fraction, wherein the residual fraction has a T10 wt. % boiling point of between 200 and 450° C.;   (c) recycling part of the residual fraction to step (a); and   (d) catalytic dewaxing of remaining residual fraction to obtain a residual base oil.   
     
     
         2 . A process Process according to  claim 1 , wherein the gas oil fraction and the heavy distillate fraction are separated in step (b) at a cut point temperature of between 300 and 400° C. 
     
     
         3 . A process according to  claim 1 , wherein the heavy distillate fraction and the residual fraction are separated in step (b) at a cut point temperature of between 450 and 600° C. 
     
     
         4 . A process according to  claim 1 , wherein the Fischer-Tropsch derived feedstock has an initial boiling point of below 400° C. and a final boiling point above 600° C. 
     
     
         5 . A process according to  claim 1 , wherein the fraction boiling above 540° C. in the feedstock to step (a) is at least 20 wt %. 
     
     
         6 . A process according to  claim 1 , wherein the residual base oil obtained in step (d) has a kinematic viscosity at 100° C. according to ASTM D-445 in the range of from 15-35 cSt. 
     
     
         7 . A process according to  claim 1 , wherein the base oil obtained in step (d) has a cloud point of between 80° C. and −60° C. as measured according to ASTM D-5773. 
     
     
         8 . A process according to  claim 1 , wherein the base oil obtained in step (d) has a pour point of below 0° C. as measured according to ASTM D-97-93. 
     
     
         9 . A process according to  claim 1 , wherein the base oil as obtained in step (d) has a Viscosity Index of between 120 and 160 as measured according to ASTM D-2270. 
     
     
         10 . A process according to  claim 1 , wherein the base oil obtained in step (d) is added to the gas oil fraction obtained in step (b). 
     
     
         11 . A process according to  claim 1 , wherein the dewaxing step is performed by means of a catalytic dewaxing process in the presence of a catalyst comprising a medium pore size molecular sieve and a group VIII metal. 
     
     
         12 . A process according to  claim 11 , wherein the molecular sieve is a MTW, MTT, TON type molecular sieve or ZSM-48 or EU-2. 
     
     
         13 . A process according to  claim 11 , wherein the Group VIII metal is platinum or palladium. 
     
     
         14 . A process according to  claim 11 , wherein the catalyst used in the catalytic dewaxing of the residual fraction comprises a MTW molecular sieve, platinum or palladium as Group VIII metal and a silica or titania binder.